It would, but it also wouldn't work anymore the way you've wired it with the workaround you had to do to get the PCF driving the optos.
Yeah, makes sense. You don't need galvanic isolation for this, so no problems there.
Of course you can...this stuff is so cheap you won't believe it. But for me that's not the motivation to forego these boards. It's that they rarely do exactly what I need; they either need additional modifications or they bring unnecessary parts, and they never are the most compact, elegant solution. I'd much rather just draft a circuit and make it into a PCB. But I do understand the attractiveness of buying ready-made modules. I used to do this too until I got tired of it.